1. Field of the Invention
The present invention relates to a shaft for golf clubs.
2. Description of the Related Art
Stability of a hit ball direction is required for a shaft for golf clubs. In particular, the tendency is strong in a comparatively short shaft. Flight distance performance is required for the shaft for golf clubs. A lightweight shaft is useful to improve the flight distance performance.
Japanese Patent Application Laid-Open No. 10-328340 (U.S. Pat. No. 6,354,957) discloses a shaft including a body layer obtained by winding a first fiber reinforced prepreg, and an adjusting layer obtained by winding a second fiber reinforced prepreg. The adjusting layer is provided at an inner side of the body layer, or in the middle of the body layer. The second fiber reinforced prepreg has a higher specific gravity and lower elasticity as compared with the first fiber reinforced prepreg. The volume of the adjusting layer is 10 to 90% based on the entire shaft. The gazette describes that a reinforcing fiber of the adjusting layer may be a glass fiber.
Japanese Patent Application Laid-Open No. 2012-245309 (US2012/0309558) discloses a shaft including a partial layer partially arranged in an axial direction of the shaft. The partial layer includes a butt end reinforced bias layer and a butt end reinforced hoop layer. In the shaft, a torsional rigidity value GIt in a point separated by 300 mm from a butt end is set to a predetermined range.
Japanese Patent Application Laid-Open No. 2003-190341 (US2003/0125125) discloses a shaft including a TIP side angle reinforced layer. In the shaft, weight saving and a low torque can be achieved. In the shaft, stability of a hit ball direction and an improvement in a flight distance can be realized.